The present invention relates to a method of combining at least two models of a common region of space to form a resultant model. Such a method may be used, for example, to improve a geological model of a region when exploring for hydrocarbon reserves.
In order to search for and guide the exploitation of hydrocarbon reserves such as oil and gas, it is known to construct geological models of the earth from measurements obtained by various techniques. These techniques include seismic surveying and the use of magnetometers and gravity measurements. Such geological models give information about the geological structure of the earth below the surface or below the seabed and allow potential commercially exploitable reserves of hydrocarbons to be identified. Such models are also used for guiding the drilling of wellbores to test for the actual presence of hydrocarbons or to be used as production wells for exploiting identified hydrocarbon reserves.
The measurements obtained by such techniques are subject to inaccuracies, for example resulting from inaccuracies in the measuring instruments or techniques involved or inaccuracies resulting from imperfect knowledge of the geology. Models obtained by different measurement techniques are subject to different levels of inaccuracies so that different models of the same region predict different locations for geological formations.
It is known to make use of geological models when drilling a well and to make measurements during the drilling process. Measurements made during drilling are generally relatively accurate whereas the uncertainties in position in geological models are relatively large. Thus, when a well is being drilled and a boundary or interface between different rock strata is detected, the well measurement is used to correct the position of the boundary in the geological model being used to guide the drilling. However, the correction which is provided by such techniques is very limited and amounts to correcting the position, such as depth, of the boundary which has been encountered and possibly providing the identical correction to points in a small region adjacent the drill bit.